The present invention is directed to inhibiting alcohol effects on cell adhesion, and more particularly to method and compound for antagonizing inhibition effects of alcohol on cell adhesion, and further to the use of alcohol inhibition antagonists in prophylaxis or treatment of toxic effects of alcohol.
Ethanol is a pleiotropic, weak central nervous system (CNS) drug (Charness et al., 1989). Ethanol potency is orders of magnitude less than that of other psychoactive drugs. This low potency indicates that the brain does not express a high-affinity ethanol receptor; rather, ethanol is believed to produce its CNS effects by interacting at millimolar concentrations with components of diverse neurotransmitter systems (Diamond and Gordon, 1997). For many years, the prevailing view was that ethanol modified synaptic activity by altering the biophysical properties of neuronal membranes, thereby disrupting indirectly the function of various membrane proteins (Goldstein, 1983). Recent research, however, suggests that ethanol interacts directly with small regions of selective neuronal proteins (Slater et al., 1993; Franks and Lieb, 1994; Harris, 1999).
The immunoglobulin neural cell adhesion molecule L1 is a multifunctional, transmembrane protein that binds to L1 molecules on adjacent cells and to selective proteins in the extracellular matrix, cell membrane, and cytoskeleton (Crossin and Krushel, 2000). L1 interactions control cell-cell and cell-matrix events that are essential for growth cone mobility, axon pathfinding, axon fasciculation, and neuronal migration. L1 binding also triggers a series of transmembrane signaling events, resulting in neurite outgrowth and changes in growth cone morphology. L1 is expressed in the developing nervous system, where it plays a critical role in CNS development (Fransen et al., 1995; Fransen et al., 1998; Demyanenko et al., 1999), and in the mature CNS, where it may be involved in learning and memory (Lüthi et al., 1994; Rose, 1995).
Mutations in the gene for L1 are associated with hydrocephalus, agenesis of the corpus callosum, cerebellar dysplasia and a variety of other brain malformations (Fransen et al., 1995). Because children with fetal alcohol syndrome have neuropathology similar to that of children with L1 mutations, we studied the effects of ethanol on L1-mediated cell-cell adhesion (Charness et al., 1994; Ramanathan et al., 1996). Clinically-relevant concentrations of ethanol inhibited L1-mediated cell adhesion in NG108-15 neuroblastoma×glioma hybrid cells, cerebellar granule cells, and selected human L1-transfected murine fibroblasts (Charness et al., 1994; Ramanathan et al., 1996; Wilkemeyer and Charness, 1998; Wilkemeyer et al., 1999). Similar concentrations of ethanol also inhibited L1-mediated neurite outgrowth in cerebellar granule cells (Bearer et al., 1999).
Structure activity analysis of various straight-chain, branched-chain, and cyclic alcohols revealed surprisingly strict structural requirements for alcohol inhibition of L1-mediated cell-cell adhesion (Wilkemeyer et al., 2000). The potency of methanol, ethanol, 1-propanol, and 1-butanol increased as a function of carbon chain length and membrane-buffer partition coefficient (Charness et al., 1994; Ramanathan et al., 1996). In contrast, 1-pentanol and higher 1-alcohols had no effect on L1-mediated cell-cell adhesion. The activity of 1-butanol, a four-carbon 1-alcohol, was abolished by the presence of a double bond between the 3 and 4 carbons; however, the presence of methyl groups at the 2 or 3 carbons was associated with an increase in potency (Wilkemeyer et al., 2000). These findings indicate that ethanol and other small alcohols inhibit L1-mediated cell-cell adhesion by binding within a well-defined, hydrophobic pocket of a target protein, possibly L1.
We believe that the existence of a specific binding pocket for ethanol would lead to the development of drugs that can block ethanol's effects. Strikingly, very low concentrations of both the five-carbon alcohol 1-pentanol and the eight-carbon alcohol 1-octanol abolished the effects of ethanol on L1-mediated cell-cell adhesion (Wilkemeyer et al., 2000). 1-Octanol also blocked the effects of ethanol on the morphology of dividing neural cells (Wilkemeyer et al., 2000) and prevented apoptosis and dysmorphology in cultured mouse embryos (Chen et al., 2001). 1-Octanol is a toxic compound that could not be used clinically. However, the identification of a single compound that blocks ethanol teratogenesis indicates the possibility of safer alcohol antagonists.
In U.S. Pat. No. 6,359,015 B1—Charness et al. (incorporated herein in its entirety by reference) a method and composition for antagonizing inhibition effects of alcohol on cell adhesion using 1-pentanol, 1-octanol, and derivatives thereof, was disclosed. The present invention identifies a new series of alcohol antagonists and examines their structure activity relation and mechanism of action.
U.S. Pat. Nos. 5,496,851; 6,169,071; and 6,169,072, are directed to method and compounds for modulating or inhibiting cell-cell-adhesion.